gis data modeling and database design (2014)

8/10/2019 GIS Data Modeling and Database Design (2014)

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Modeling and Representing

Geographic Situation andGIS Database Design

Nama Raj Budhathoki, Ph.D.


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Nama Raj Budhathoki Apex GIS course - 2014

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Model can be in different forms


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Dictionary meaning of Model

Miniature representation of an object,

system, process or phenomena so thatits certain aspects of interest can be

analyzed/studied

Can be picture, mathematical, physical,

diagram or other


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Geospatial Data Modeling

Process of extracting and representing

geospatial objects or phenomena in

relation to their location in geographic

space and time

This process influences the type of

questions a GIS can answer


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Paper Map as a Model of Real World

Data capture

Representation

Visualization


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But!..Paper Map is an inefficient

model of Real World

Difficult to change andanalyze information

Fixed scale Require large storage space

High back up, production,reproduction and transfercost

Features in map fade overtime and use

Shrinkage bringsmeasurement inaccuracies


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How can we represent such a

complex world in the computer?


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Two Views

Continuous phenomena(Elevation, temperature,

pollution etc.)

Discrete Objects withclear boundary, shape

and size (Land parcels,

buildings, roads etc.)


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Geospatial Data Models

We use different models to

represent two views ofgeospatial phenomena: Feature

(vector)for discrete objects and

Field (Raster) for continuous

phenomena


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Stages of Geospatial Data Modeling

Representation

in the computer

Extraction ofthe real world

Realworld

Human World (Real World)

Computer World (Virtual World)(0s and 1s)


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Different Levels of Data Modeling

Conceptual Modeling

Physical Modeling

Logical Modeling

Realworld

What to

extract?

How to represent andstore in computer?


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Conceptual Data Model

Certain concept (domain) is used toselectively extract the real world from its

infinite complexity.Consists of the following steps (Zeiler1999):

Model the user and use view

Define entities and their relationships

Identify representation of entities


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Conceptual Date Model:Model use and users view

Identify the functions GIS is to support

eg.Land Use Planning

Identify the data required to support tothese functions

eg. Land Records, Environmental data,

Transportation data


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Conceptual Model:Define and describe entities

Identify entities

Entities are distinguishable objects; Something about which data is kept

Describe entities

Attributes associated with an entity

Key Attribute - uniquely identify an entity


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Conceptual Model:Identify relationships and attributes

Identify and describe relationships

among these entities

One-to-One (1:1)

One-to-Many (1:N)

Many-to-Many (N:M)

Document the entities andrelationships in diagram (ERD)


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Diagrammatic Example of Land

Records

More on Next Week


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Conceptual Model:Identify representation of entities

Point

LineArea

Raster

Image Surface

Object

Discrete Features

Continuous Phenomena

Terrain

Non-geographic entity


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Summary

Data capture

Data storage

and management

Data Visualization

Database

gis data modeling and database design (2014)

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